The changelog for b1 was missing. While you wait for the next relase, here you can find it.

New multithreading rendering architecture. Class IRenderer split into IView (for the main thread) and IRenderer (for the renderer thread, if any). More information at the rendering tutorial.

Base class for renderers have been simplified. With 1.3 we expect all our clients to provide custom renderer implementations. Shouldn't take more than 2 - 3 day to implement one following our reference implementation.

Our official runtimes no longer provide renderer implementations. It must be implemented by client code. We will provide reference implementations for all our platforms within the SDK. D3D11 and GL/GL_ES provided in this version.

For now, the renderer API is not exposed to C#. Soon or later it will be, that way you can implement a renderer using only C#. But for now, the GL and D3D11 renderers are included inside the C# SDK binaries and you have functions to initialize each API in the same way you are doing for 1.2: